Independent-effect comparison of five crosslinking procedures for Progressive Keratoconus based on Keratometry and the ABCD Grading System using Generalized Estimating Equations (GEE)

Abstract

Purpose Corneal collagen crosslinking (CXL) is an effective treatment for progressive keratoconus. Multiple CXL modalities are clinically available. The present study compared the 1 year outcomes of five types of CXL procedures for progressive keratoconus in a Chinese population using generalized estimating equations (GEE). Methods This retrospective study included 239 eyes in 171 patients with keratoconus who underwent CXL and were followed up for 1 year. Five CXL procedures were assessed, including Accelerated Transepithelial CXL, Iontophoresis CXL for 10 min, CXL plus phototherapeutic keratectomy (CXL-plus-PTK), High-Fluence Accelerated CXL, and Accelerated CXL. Patients treated with the Accelerated CXL procedure represented the reference group. Primary outcomes were visual acuity change, spherical equivalence, endothelial cell density, mean keratometry (Kmean), maximum keratometry (Kmax), minimum corneal thickness (MCT), and the ABCD Grading System, consisting of A (staging index for ARC; ARC = anterior radius of curvature), B (staging index for PRC, PRC = posterior radius of curvature), and C (staging index for MCT) values 1 year postoperatively compared to baseline. Secondary outcomes were corrected GEE comparisons from each procedure versus the Accelerated CXL group. Results The Accelerated Transepithelial CXL group had lower performance than the Accelerated CXL group according to Kmean and Kmax. The CXL-plus-PTK group performed significantly better than the reference group as reflected by Kmax (β = -0.935, P = 0.03). However, the CXL-plus-PTK group did not perform as well for B and C, and the Iontophoresis CXL group performed better for C. Conclusions The CXL-plus-PTK procedure was more effective than the Accelerated CXL procedure based on Kmax, and the Iontophoresis CXL procedure performed better on the C value based on the ABCD Grading System.

Short-Term Effect of Conventional Versus Accelerated Corneal Cross-Linking Protocol on Corneal Geography and Stability

“…In the literature, only a few studies evaluated the applicability of the ABCD staging system in monitoring the efficacy of the standard procedure. In contrast, only one recently published retrospective study investigated its utility in evaluating accelerated protocols and compared the effectiveness of different protocols regarding the ABCD grading system [ 8 , 39 , 40 , 41 , 42 , 43 ]. Danesh and coauthors showed no significant changes in parameters A and D, while parameters B and C significantly increased one year after conventional CXL [ 8 ].…”

“…Contrary, there were no significant changes in parameter B. Parameter C significantly progressed while D remained stable one year after the procedure. Recently, in 2023, a retrospective study was published, the first to our knowledge to evaluate the efficacy of five different accelerated protocols regarding the ABCD staging system one-year post-treatment [ 43 ]. The results showed that parameters A and B decreased in the Iontophoresis CXL group.…”